Directional seat valve

ABSTRACT

A directional seat valve has a valve housing having a pressure connector for supplying pressure medium to the valve housing, a tank connector for returning pressure medium to a pressure medium tank, and a working connector for supplying pressure medium to a working device. The valve housing has a valve bore. Shaped parts with a valve seat are press-fit into the valve bore. A valve body in the valve bore controls together with the valve seats the pressure medium flow between the connectors. The seat valve is assembled by press-fitting the first shaped part with its valve seat into the valve bore, inserting the valve body into the valve bore, and press-fitting the second shaped part with its valve seat into the valve bore. The press-fit insertion depth of the first and second shaped parts in the valve bore is selected based on the position of the armature push rod.

[0001] This application is a division of application Ser. No.09/510,545, filed Feb. 22, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to a directional seat valve comprising avalve body which is arranged in a valve bore and biased against at leastone valve seat. It is lifted off the valve seat for connecting apressure connector to a tank connector or a work connector. Theinvention furthermore relates to a method for assembling such adirectional seat valve.

[0004] 2. Description of the Related Art

[0005] Such directional seat valves have a valve housing with an axialbore in which a valve body is moveably arranged. The valve body isbiased by a pressure spring against the valve seat. Upon surpassing apredetermined pressure at the inlet connector, the valve body is liftedoff the valve seat and moved into an opening position in which the inletconnector is connected to an outlet connector, for example, a workconnector or a tank connector.

[0006] In the publication “Der Hydraulik Trainer”, vol. 1, MannesmannRexrodt GmbH, 1991, p. 203, a directional seat valve is described inwhich one valve body has correlated therewith two valve seats so that,depending on the position of the valve body, the inlet or pressureconnector is connected to a working connector or the working connectoris connected to the tank connector. This valve is provided with negativeoverlap so that in an intermediate position, in which the valve body isresting neither against one nor the other valve seat, all threeconnectors communicate with one another.

[0007] In particular, directional seat valves with smaller nominaldiameter are generally directly controlled by a mechanically actingdevice, for example, a solenoid so that the valve body can be broughtinto a predetermined switching position or can be maintained in it.

[0008] The problem with such directional seat valves is that themagnetic operating point of the solenoid must be adjusted relativelyprecisely to the axial position of the valve seat so that switching ofthe solenoid acts without play and without delay onto the valve body.

[0009] This means that the components of the mechanical connecting chainbetween the solenoid and the valve body must be exactly adjusted withrespect to their tolerances to the magnetic operating point of thesolenoid.

SUMMARY OF THE INVENTION

[0010] It is therefore an object of the present invention to provide adirectional seat valve and a method for assembling the directional seatvalve in which the process-technological and assembly-technologicalexpenditures are reduced in comparison to conventional solutions.

[0011] In accordance with the present invention, this is achieved forthe directional seat valve in that the valve seat is provided on ashaped part which is inserted with press-fit into the valve bore.

[0012] The directional seat valve according to the present inventioncomprises: a valve housing having a pressure connector configured tosupply a pressure medium to the valve housing, a tank connectorconfigured to return the pressure medium to a pressure medium tank, anda working connector configured to supply the pressure medium to aworking device; a valve bore arranged in the valve housing; one or moreshaped parts each configured to be press-fit into the valve bore andeach having a valve seat; a valve body arranged in the valve bore andconfigured to cooperate with the valve seat of the one or more shapedparts for controlling flow of the pressure medium from the pressureconnector to at least one of the tank connector and the workingconnector.

[0013] Moreover, in accordance with the present invention, this isachieved in connection with the method in that the first shaped part ispress-fit into the valve bore for forming the first valve seat, whereinthe press-fit insertion depth is selected depending on the position ofthe solenoid armature push rod; the valve body is then inserted; and thesecond shaped part is subsequently press-fit into the valve bore forforming the second valve seat, wherein the press-fit insertion depth isagain selected depending on the position of the armature push rod.

[0014] The method according to the present invention for assembling adirectional seat valve actuated by an armature push rod of a solenoidcomprises the steps of: press-fitting a first shaped part with a firstvalve seat into a valve bore and selecting a press-fit insertion depthin the valve bore based on a position of an armature push rod; insertinga valve body into the valve bore; and press-fitting a second shaped partwith a second valve seat into the valve bore and selecting a press-fitinsertion depth of the second shaped part in the valve bore based on theposition of the armature push rod.

[0015] With the directional seat valve according to the invention thevalve seat body is realized by a shaped part which is inserted withpress-fit into a valve bore of the valve housing. The press-fitinsertion depth depends on the actual magnetic operating point of theemployed solenoid so that an optimal response of the valve to theswitching of the solenoid is ensured. The press-fit insertion depth canbe adjusted according to the invention, for example, by suitable toolswhich are provided with stops determining the press-fit insertion depth.Upon insertion of the shaped parts by means of the tools, the stop ofthe tools can be brought into contact with the armature push rod. Due tothe exact correlation between the magnetic operating point and theposition of the valve seat, it is no longer required to provide alinearization of the solenoid used for switching the directional seatvalve so that the configuration of the inventive directional seat valveis further simplified.

[0016] The inventive configuration of the valve seat in the form of ashaped part inserted with press-fit into the valve bore can be employedespecially advantageously for so-called single ball valves in which thevalve body is arranged between two valve seats so that, depending on thecontrol action, the three connectors can communicate with one another ina predetermined connecting pattern.

[0017] The control action for the valve body is preferably realized by asolenoid. In an especially preferred embodiment, the valve body isbiased against one of the valve seats by a push rod of the solenoid thatis acted on by a pressure spring. Upon actuation of the solenoid, thepush rod is lifted off the valve body against the force of the pressurespring so that the valve body can be moved against the other valve seat.

[0018] The manufacture and assembly of the shaped part are especiallysimple when the shaped part is deep-drawn from sheet metal. The outerdiameter of the shaped part, which is expediently cup-shaped, ispreferably selected such that it is over-sized relative to the valvebore so that the shaped part can be inserted with press-fit.

[0019] The configuration of the valve seat in the shaped part isespecially simple when in the bottom of the cup-shaped part an outwardlyor inwardly projecting portion is formed which is provided with apenetration forming the valve seat.

[0020] Inventively, this valve seat is fine-machined by stamping with avalve body having a diameter that is greater than that of the actuallyemployed valve body so that a precise contact and seat surface for thevalve body is provided.

[0021] For a single ball valve the valve body is preferably guided by aguide sleeve which is positioned between the two press-fit shaped partsand which prevents a radial deflection of the valve body. In this way, asafe sealing and closure of the valve seat is ensured.

[0022] The two shaped parts for a single ball valve are preferablyconfigured such that they can be inserted into the valve bore from oneend of the valve housing and have substantially the same orientationalposition, i.e., are pointed with their cup bottom toward the solenoid.In order to facilitate inflow and outflow through radial connectors ofthe valve housing, the shaped parts are radially stepped so that thepressure medium flow to the valve seat is facilitated. The push rod ofthe solenoid is designed preferably such that it penetrates theneighboring valve seat and biases the valve body in the direction towardthe other (remote) valve seat.

[0023] The valve housing can have an especially compact configurationwhen the coil member of the solenoid is radially widened toward thevalve portion so that a projecting end portion of the valve housing canbe inserted into the radially widened portion.

[0024] Other advantageous embodiments of the invention will becomeapparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING

[0025] In the drawing:

[0026]FIG. 1 is a section view of a directly controlled directional seatvalve according to the present invention;

[0027]FIG. 2 is a detail view of the directional seat valve of FIG. 1;

[0028]FIG. 3 is a detail view of a valve seat of the directional seatvalve of FIG. 1;

[0029]FIG. 4 is a representation of a tool for correctly positioning thevalve seat; and

[0030]FIG. 5 is a second embodiment of the directly controlleddirectional seat valve according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031]FIG. 1 shows a section of a directly controlled 3/2 directionalseat valve 1 (the designation 3/2 refers to the number of connectorsavailable, i.e., three, and the number of connectors, i.e., two, to berespectively connected for operation). It has a cartridge configurationwith a valve housing 2 having a valve bore 4 into which a pressureconnector P, a working connector A, and a tank connector T open. Thepressure connector P opens axially into the valve bore 4, while the twoconnectors A and T are embodied as radial star bores. The 3/2directional seat valve 1 is a so-called single ball valve and has avalve body 6 correlated with two valve seats 8, 10. These valve seats 8,10 will be described in more detail at a later point.

[0032] The base position represented in FIG. 1 shows the valve body 6being pushed by a push rod 12 against the valve seat 8 to the right inFIG. 1. This push rod 12 is a unitary (monolithic) part of the armature14 of a solenoid 16 and is biased by a pressure spring 18 into itscontact position against the valve body 6.

[0033] The solenoid 16, which will be explained in more detail in thefollowing, is embodied as a pulling magnet so that the solenoid 16 willlift the push rod 12 off the valve body 6 against the force of thepressure spring 18 when supplied with current.

[0034] The solenoid 16 has a deep-drawn housing 20 in which the coilmember 22 with its coil 24 is mounted.

[0035] The coil member 22 has a plug-in 26 at one end portion (to theleft in FIG. 1) for supplying current to the solenoid 16. A metal disc28 is embedded by injection molding into the coil member 22.

[0036] According to FIG. 1, the coil member 22 has an axial recess 30that opens at its right end face and receives a tube 32. This tube 32receives a pole core (magnet core) 34 having one end face restingagainst the metal disc 28 and having a leaf or thin plate 36 made of amagnetically non-conducting material provided at its other end face. Themagnet core 34 is seal tight inserted into the tube 32. An axial blindbore 43 a, having an inner end face against which the pressure spring 18is resting, is provided in the right end portion of the pole core 34, asshown in FIG. 1.

[0037] As can be seen also in FIG. 1, the tube 32 and the coil member 22are radially widened in the area of the leaf 36, beginning with theslanted shoulders 38 and 32 a. The radially widened portions 38 a, 32 bof the coil member 22 and of the tube 32 are provided for receiving aprojecting end portion 40 of the valve housing 2 by which the valvehousing 2 is connected to the solenoid 16, i.e., more precisely, to thecoil member 22 and the solenoid housing 20.

[0038] The armature 14 is guided in the axial bore 4 penetrating thevalve housing 2 and has a radially widened end portion 14 a facing thepole core 34. The radially widened end portion 14 a of the armature 14is guided with play in the axial bore 4. The armature 14 is penetratedby a central bore 42 which widens in the direction toward the left endface in FIG. 1. The pressure spring 18 engages the annular end face 42 aprovided by the widened portion of the bore 42.

[0039] In the area of the radially widened portion 14 a of the armature14 an annular groove 44 with radial bores 46 opening into the centralbore 42 is provided. The armature 14 is tapered at the end portionfacing the valve seats 8, 10, and this tapered end portion defines thepush rod 12. In this tapered portion a transverse bore 48 is provided inwhich the central bore 42 ends. The transverse bore 48 opensapproximately in the area of the tank connector T into the valve bore 4.

[0040] The spring chamber for receiving the pressure spring 18 and thespace defined by the annular groove 44 and the neighboringcircumferential wall of the valve housing 2 are connected via the bores42, 46, 48 and the tank connector T to the pressure medium tank orreservoir so that in these areas only a negligible tank pressure isbuilt up but lubrication of the movable parts of the solenoid 16 isensured.

[0041] Instead of the bores 42, 46, 48, longitudinal grooves can beprovided at the outer circumference of the armature 14 in order toconnect the spring chamber to the tank connector T.

[0042] The attachment of the directional valve 1 of FIG. 1 to a housingis realized by the fastening flange 50.

[0043] The hydraulic portion of the solenoid-operated directional valve1 is represented in FIG. 2 on an enlarged scale. Three O-rings 52 arearranged at the outer circumference of the valve housing 2 for a sealtight arrangement of the connectors P, A, and T relative to one another.The two valve seats 8, 10 for the ball-shaped valve body 6 areinventively embodied as two deep-drawn shaped parts which in firstapproximation are basket or cup-shaped. The valve seat 8 is provided atthe first shaped part 54, and the valve seat 10 is provided at thesecond shaped part 56. The shaped parts 54, 56 are deep-drawn sheetmetal parts, preferably sheet steel parts, which have a basket-shaped ora cup-shaped configuration with a cup bottom 54 b, 56 b and a cupsidewall 54 a, 56 a. The outer diameter D of the shaped parts 54, 56 isslightly greater than the diameter d of the valve bore 4 (see FIG. 2) sothat the shaped parts 54, 56 are inserted with press-fit into the valvebore 4.

[0044] In principle, the shaped parts could also be fastened in otherways known to a person skilled in the art to the valve bore 4.

[0045] The first shaped part 54 represented to the right in FIG. 2 has ahub-shaped outwardly projecting portion 58 at the cup bottom 54 b. Thebottom of the outwardly projecting portion 58 is provided with the valveseat 8 that is in the form of an axial penetration. As can be seen alsoin FIG. 2, the first shaped part 54 tapers via a slanted wall 60 in thearea of the working connector A.

[0046] According to FIG. 2, the curved slanted wall 60 is arranged suchthat the flow between the working connector A and the valve bore 4 isdeflected toward the valve seats 8, 10 so that the flow resistance isreduced. Moreover, the slanted wall 60 simplifies the manufacture (deepdrawing) and the insertion of the shaped parts 54, 56.

[0047] The second shaped part 56 has in general the same configurationas the first shaped part 54, wherein at the cup bottom 56 b (the leftend face in FIG. 2) of the shaped part 56 an inwardly projecting portion62 is formed instead of the outwardly projecting portion 58 of theshaped part 54. Accordingly, the hub-shaped projection according to thisembodiment formed by the inwardly projecting portion 62 extends into theinterior of the basket-shaped or cup-shaped part 56 while the outwardlyprojecting portion 58 of the first shaped part 54 projects away from thecup bottom 54 b and the interior of the cup-shaped part 54.

[0048] The inwardly projecting portion 62 and the outwardly projectingportion 58 have the same outer diameter and support, as shown in FIG. 2,a plastic sleeve 64. The plastic sleeve 64 engages with one end theinwardly projecting portion 62 and with the oppositely arranged end theoutwardly projecting portion 58. The plastic sleeve 64 provides an axialguiding action for the valve body 6. The valve body 6 is received withplay in the interior of the plastic sleeve 64 so that flow past thevalve body 6 is possible within the plastic sleeve 64. The wall of theplastic sleeve 64 is provided with penetrations 66 so that the pressuremedium can pass into the interior of the plastic sleeve 64.

[0049] The plastic sleeve 64 prevents the lateral deflection of thevalve body 6 so that an axial orientation with respect to the valveseats 8, 10 is realized. Such a radial deflection of the valve body canoccur in unfavorable operating conditions. This could be, for example,the case when at the connector P no or only minimal pressure is presentso that the valve body is not secured by pressure medium flow about itscircumference in its radial position. If no plastic sleeve 64 werepresent, a radial deflection of the valve body 6 could result also foraccelerations occurring perpendicularly to the valve axis.

[0050] The press-fit insertion depth of the two shaped parts 54, 56 intothe valve bore 4 depends on the magnetic operating point of the solenoid16. Therefore, the magnetic operating range of the solenoid 16 isdetermined by a series of experiments before assembly of the inventivedirectional valve 1, and as a function of the experimentally determinedoperating range the press-fit insertion depth is determined. With thismeasure it is ensured that the solenoid 16 is controlled within anoptimal operating range so that a fast response of the valve is ensured.

[0051] Based on the minimal stroke of the armature 14 and the exactdetermination of the position of the valve seats 8, 10 relative to themagnetic operating range, it is no longer needed to provide a partiallinearization of the characteristic line of the solenoid 16. Such apartial linearization can be achieved, for example, by of radialdeflection of the magnetic field lines which cause, in turn, thepresence of forces acting in the radial direction. This means that sucha partial linearization requires, on the one hand, a more complexconfiguration of the solenoid and, on the other hand, results in forcesacting in the radial direction onto the armature and the valve body.This decreases the response behavior of conventional directional valvesin comparison to the solution according to the present invention withoutpartial linearization.

[0052] According to FIG. 4, suitable tools 80 are provided for theinsertion of the two shaped parts 54, 56. The tool 80 for insertion ofthe shaped part 56 positioned adjacent to the push rod is provided atits end face with a circumferential annular collar 82 which can bebrought into contact against the inner end face of the shaped part 56.The adjustment of the press-fit insertion depth is realized by a contactsurface 84 of the centrally arranged adjusting pin 86 which can bebrought into contact at the end face of the armature push rod 12. Theaxial spacing X of the end face of the annular collar 82 to the contactsurface 84 determines thus the press-fit insertion depth of the shapedpart 56. In this way, the tool 80 forces the shaped part 56 into theaxial bore 4 until the abutment or contact surface 84 comes to restagainst the push rod 12. In this way, manufacturing tolerances of thesolenoid can be simply compensated with a corresponding machining of thetool 80. The insertion of the shaped part 54 is then realized either asa function of the axial position of the shaped part 56 or by a tool,embodied according to the representation of FIG. 4, as a function of theactual position of the armature push rod 12 wherein the adjusting pin 86projects axially past the annular collar 82.

[0053] During assembly, first the second shaped part 56 is placed ontothe corresponding tool 80 and is then brought into the desired press-fitposition. Subsequently, the plastic sleeve 64 and the valve body 6 areinserted, and the second shaped part 54 is then press-fit into the valvebore 4 with a further tool 80. The press-fit insertion depth isdetermined again by a suitable design of the tool 80.

[0054]FIG. 3 shows an enlarged representation of the valve seat 8 of thefirst shaped part 54. As can be seen in the Figure, the valve seat 8 hasa contact surface 72 which is produced by stamping with a stampingmember 74 (represented by dashed lines in FIG. 3), for example, a valvebody with a greater diameter than the valve body 6 of the directionalvalve. With this pre-stamping action the roundness of the valve seat 8(10) is ensured.

[0055] When no current is supplied to the coil 24, the valve body 6 isbiased by the push rod 12, the armature 14, and the pressure spring 18against the valve seat 8 so that the connection from the pressureconnector P to the working connector A is interrupted. In this position,represented in FIGS. 1 and 2, the valve body 6 is lifted off the valveseat 10 so that the connection from the working connector A to the tankconnector T is open. The pressure spring 18 is configured such that thevalve body 6, upon surpassing a maximum pressure, is lifted off thevalve seat 8 so that a pressure limitation function is realized. Uponlifting of the valve body 6 from the valve seat 8, initially all threeconnectors P, A, and T communicate with one another.

[0056] When current is supplied to the solenoid 16, a magnetic field isbuilt up that causes an axial movement of the armature 14 to the left inthe representation of FIG. 1. The field lines of the magnetic fieldpenetrate the deep-drawn housing 20, the disc 28, the pole core 34, thegap between the pole core 34 and the armature 14, the armature 14itself, and the projecting end position 40 of the valve housing 2.

[0057] The axial movement of the armature 14 causes the push rod 12 tobe removed from the valve body 6 so that the valve body 6 is forced bythe pressure present at the pressure connector P against the valve seat10. The connection from the working connector A to the tank connector Tis closed while the connection from the pressure connector P to theworking connector A is opened. The pressure medium can flow from thepressure connector P through the open valve seat 8 and the penetrations66 in the plastic sleeve 64 to the working connector A. The consumer isthus supplied with pressure medium. This consumer can be, for example, acylinder which actuates an automated automobile transmission.

[0058] The valve is realized with negative overlap so that within atransition area all three connectors P, A, and T communicate with oneanother.

[0059] Thus, the present invention discloses a solenoid-actuateddirectional valve in which the valve seat is realized by a cup-shapedpart which is inserted into the valve bore.

[0060] The directional seat valve represented in FIG. 5 differs from theabove disclosed embodiment in that the armature 14 and the push rod 12are not an integral or monolithic part but are separate components. Thearmature 14 has a central bore 42 which penetrates the armature 14axially and in which the push rod 12 is secured by press-fit. The wallof the central bore 42 has at least one longitudinal groove 88 by whichthe spring chamber 90, in which the pressure spring 18 is mounted, isconnected to the tank connector T.

[0061] Since the armature 14 and the push rod 12 are separatecomponents, the bias of the pressure spring 18 can be adjusted simplyand precisely by pressing the push rod 12 into a force-dependentposition.

[0062] The push rod 12 is forced into the armature 14 until the force ofthe pressure spring 18 upon contact of the armature 14 on the stop hasreached a predetermined force. Thus, the adjusting tolerance for thepressure securing action is very minimal. Furthermore, cost savings areachieved in regard to the individual parts because reduced requirementswith regard to coaxiality are to be met with respect to the bushing aswell as the armature 14.

[0063] The pole core 34, in contrast to the previous embodiment,comprises an axial bore 92 penetrating it centrally. The cylindricalpart 94 of the tube 32 projects into the bore 92. The part 94 is of acup-shaped configuration. The pressure spring 18 rests against thebottom of the cylindrical part 94. The bottom is positioned at a spacingfrom the metal disc 28 against which the pole core 34 rests.

[0064] The directional valve is otherwise of the same configuration asthe embodiment according to FIGS. 1 through 4.

[0065] While specific embodiments of the invention have been shown anddescribed above in detail to illustrate the inventive principles, itwill be understood that the invention may be embodied in different wayswithout departing from such principles.

What is claimed is:
 1. A method for assembling a directional seat valveactuated by an armature push rod (12) of a solenoid, wherein shapedparts (54, 56) are positioned within a valve bore (4) and each define avalve seat (8, 10), wherein a valve body (6) is positioned in the valvebore (4) and contacts selectively one of the valve seats (8, 10)provided on the shaped parts (54, 56), respectively, said methodcomprising the steps of: press-fitting a first shaped part (56) with afirst valve seat (10) into a valve bore (4) and selecting a press-fitinsertion depth in the valve bore (4) based on a position of an armaturepush rod (12); inserting a valve body (6) into the valve bore (4);press-fitting a second shaped part (54) with a second valve seat (8)into the valve bore (4) and selecting a press-fit insertion depth of thesecond shaped part in the valve bore (4) based on the position of thearmature push rod (12).
 2. The method according to claim 1 , furthercomprising the step of fine-machining the first and second valve seats(8, 10) by stamping the first and second shaped parts (54, 56),respectively, by means of a stamping member (47).